Worker in study somewhere in Switzerland? (6)
I believe the answer is:
canton
'somewhere in switzerland?' is the definition.
(Swiss administrative subdivision)
'worker in study' is the wordplay.
'worker' becomes 'ant' (worker is a type of ant).
'in' means one lot of letters goes inside another.
'study' becomes 'con' (con can informally mean to study).
'ant' put within 'con' is 'CANTON'.
(Other definitions for canton that I've seen before include "Old 5 [CHINESE] city" , "It cannot be in Switzerland" , "Old Chinatown" , "Swiss state" , "Political region in Switzerland" .)